Quasielastic ρ0 electroproduction on the proton at intermediate energy: Role of scalar and pseudoscalar meson exchange

We present a detailed analysis of rho(0) electroproduction at intermediate energy for quasielastic knockout kinematics. The approach is based on an effective Lagrangian which generates exchanges of scalar, pseudoscalar, axial-vector, and tensor mesons. The specific role of mesons with different values for J(PC) is analyzed. We show that the pi(0) exchange amplitude and its interference terms with eta(eta') and f(1) exchanges dominate in the transverse part of the cross section sigma(T). The main role plays the pi(0) -> rho(0) M1 spin transition when coupling the virtual photons to the nucleon. In contrast, the longitudinal cross section sigma(L) is generated by a series of scalar meson exchanges. To extract the dominant term, more detailed information on the inner structure of scalar mesons is required. It turns out that recent data of the CLAS Collaboration on sigma(L) and sigma(T) can be described with reasonable accuracy if one proposes the quarkonium structure for the heavy scalar mesons (M >= 1.3 GeV). On this basis the differential cross sections d sigma(L)/dt and d sigma(T)/dt are calculated and compared with the latest CLAS data.